Add sgx_tstd::prelude::{rust_2015,rust_2018,rust_2010}

sgx_tstd/build.rs

@@ -51,6 +51,12 @@ fn main() {
     if let Some(true) = is_min_date("2021-02-07") {
         println!("cargo:rustc-cfg=derive_macros");
     }
+
+    // nightly-2021-03-11 (rustc 2021-03-10)
+    // https://github.com/rust-lang/rust/commit/1ab9fe5d44860050232438967bbbf9bdc35dbde1
+    if let Some(true) = is_min_date("2021-03-10") {
+        println!("cargo:rustc-cfg=enable_prelude_version");
+    }
 }
 
 // code below copied from crate version_check

sgx_tstd/src/lib.rs

@@ -81,6 +81,7 @@
 #![feature(needs_panic_runtime)]
 #![feature(once_cell)]
 #![feature(panic_unwind)]
+#![cfg_attr(enable_prelude_version, feature(prelude_2021))]
 #![feature(prelude_import)]
 #![feature(ptr_internals)]
 #![feature(raw)]

sgx_tstd/src/prelude/mod.rs

@@ -30,3 +30,33 @@
 //! On a technical level, Rust inserts
 //!
 pub mod v1;
+
+/// The 2015 version of the prelude of The Rust Standard Library.
+///
+/// See the [module-level documentation](self) for more.
+#[cfg(enable_prelude_version)]
+pub mod rust_2015 {
+    #[doc(no_inline)]
+    pub use super::v1::*;
+}
+
+/// The 2018 version of the prelude of The Rust Standard Library.
+///
+/// See the [module-level documentation](self) for more.
+#[cfg(enable_prelude_version)]
+pub mod rust_2018 {
+    #[doc(no_inline)]
+    pub use super::v1::*;
+}
+
+/// The 2021 version of the prelude of The Rust Standard Library.
+///
+/// See the [module-level documentation](self) for more.
+#[cfg(enable_prelude_version)]
+pub mod rust_2021 {
+    #[doc(no_inline)]
+    pub use super::v1::*;
+
+    #[doc(no_inline)]
+    pub use core::prelude::rust_2021::*;
+}

xargo/sgx_tstd/build.rs

@@ -52,6 +52,12 @@ fn main() {
     if let Some(true) = is_min_date("2021-02-07") {
         println!("cargo:rustc-cfg=derive_macros");
     }
+
+    // nightly-2021-03-11 (rustc 2021-03-10)
+    // https://github.com/rust-lang/rust/commit/1ab9fe5d44860050232438967bbbf9bdc35dbde1
+    if let Some(true) = is_min_date("2021-03-10") {
+        println!("cargo:rustc-cfg=enable_prelude_version");
+    }
 }
 
 // code below copied from crate version_check